The iodates of scandium

A dihydrate, a monohydrate, and three polymorphs of the anhydride Sc(IO₃)₃ have been prepared and studied. Sc(IO₃)₃·2H₂O was prepared by gel growth and by precipitation and evaporation at room temperature. The γ-anhydride can be crystallized from boiling water or nitric acid solution. The other compounds are formed on heating the dihydrate, which also dehydrates very slowly at room temperature. The α-anhydride is amorphous. The β-anhydride generates second harmonics, with about twice the efficiency of quartz. In addition differential thermal analysis (DTA), thermogravimetric analysis (TGA), infrared absorption, and powder X-ray diffraction results are presented.